Treatment of hydrocarbon oils



Sept, 18, 193 4.

J. G. ALTHER 1,974,295

TREATMENT OF HYDROCARBON OILS Filed Dec. 19. 1931 JOSEPH G; ALTHER Patented Sept.: 18, 1934 Lass 1,974,295 TREATMENT OF HYDROCARBON OILS Joseph G. Alther, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a

corporation of South Dakota Application December 19, 1931, Serial No. 582,019

3 Claims.

This invention relates to the treatment of hydrocarbon oils, and more particularly refers to an improved process and apparatus for the conversion of hydrocarbon oils, primarily for the purpose of producing substantial yields of more desirable light products, such as motor fuel of high anti-knock value, with coke and gas as byproducts. The invention has particular reference to a continuous cracking process wherein the products are low boiling distillates coke and gas and wherein the coke is formed in a relatively low pressure auxiliary zone permitting its continuous removal therefrom.

The primary principles of the present invention comprise improvements to cracking processes which comprise subjecting residual oil, resulting from the conversion of hydrocarbon oil, in said process to further heat treatment in a separate conjointly operated zone for the purpose of eiiecting its reduction to substantially dry coke or carbonaceous material and returning condensed distillate resulting from said coking operation to said cracking system as a cooling medium to substantially prevent coking in said cracking system and to increase the yields, particularly of relatively light liquid products, from the cracking operation.

The invention contemplates the use of any suitable method of reducing the residual oil from the cracking system to coke or carbonaceous residue in a zone separate from that in which it is produced and in the preferred embodiment of the invention hereinafter illustrated and more fully described the coking zone comprises an externally heated rotary retort to which the residual oil may be continuously supplied and from which the coke or carbonaceous residue may be continuously withdrawn. Vapors resulting from the coking operation may be subjected to fractionation, their heavier components which are condensed by said fractionation being returned to the heating element of the cracking system for further conversion while only their lighter components which are subsequently condensed are returned to the cracking system to effect cooling of materials therein or, if desired, vapors from the coking zone may be subjected to condensation and cooling without fractionation, total condensed components being returned to the crack- 5G ing system to efiect cooling and to be. further converted.

A more specific embodiment of the invention may comprise subjecting a hydrocarbon oil to conversion'conditions in a heating element, in-

troducing the heated oil into an enlarged reaction zone, directing both vaporous and non-vaporous products from said reaction zone to a reduced pressure vaporizing zone wherein the residual oil is further vaporized and separated from the vaporous products, subjecting vapors m from said reduced pressure vaporizing zone to fractionation, returning the insufficiently converted components of the vapors which are condensed by said fractionation, to said heating element for further conversion, subjecting the relatively light desirable components of the vapors to condensation and cooling and collecting the resulting products, withdrawing residual oil which remains unvaporized in said reduced pressure vaporizing zone therefrom to further heat 7 treatment in an externally heated rotary retort by means of which its remaining volatile components are substantially vaporized, leaving a substantially dry carbonaceous residue, subjecting vapors from said coking retort to fractionas tion, returning their relatively heavy condensed components to said heating element for further" conversion, subjecting their relatively light components to condensation, cooling and collection and returning a portion or all of the condensate to the cracking system to cool and arrest or substantially retard conversion of the products passing from said reaction chamber to said vaporizing chamber.

The attached diagrammatic drawing illustrates one specific form of apparatus embodying the principles of the present invention and the following description of the drawing includes a description of the process of the invention as it may be practiced in the apparatus illustrated.

Raw oil charging stock for the system may be supplied through line 1 and valve 2 to pump 3, from which it is fed through line 4 and may pass, all or in part, through line 5, valve 6 and line '7 to heating element 8. If desired, all or a portion of the raw oil may be directed from pump 3 through line 4, line 9 and valve 10 into fractionator 11; being preheated in this zone by direct contact with the relatively hot ascending vapors, serving to assist their fractionation and passing, together with their insufiiciently converted components which are condensed in the fractionator, through line 12 and valve 13 to pump 14. Pump 14 supplies the reflux condensate or reflux condensate and raw oil, from fractionator 11 through line 7 and valve 15 into heating element 8.

Heating element 8 is located in a furnace 16 of any suitable form and the oil passing through this zone is heated to the desired temperature, preferably at a substantial superatmospheric pressure. 110

The heated oil is discharged through line 17 and valve 18 to reaction chamber 19.

Reaction chamber 19 is also preferably maintained at a substantial superatmospheric pressure and materials remaining vaporized in this zone are subjected to continued conversion for a predetermined time while non-vaporous products pass more rapidly to the lower portion of chamber 19 to be withdrawn therefrom substantially as fast as they collect, passing together with vaporous products from the chamber through line 20 and valve 21 to vaporizing chamber 22.

Chamber 22 is preferably maintained at a substantially reduced pressure relative to that employed in chamber 19 by means of which the nonvaporous residual oil introduced into this zone is subjected to further vaporization, the remaining non-vaporous residual oil being separated from the vapors in this zone. Vapors from chamber 22 pass through line 23 and valve 24 to fractionation in fractionator 11 by means of which their relatively heavy insufiiciently converted components are condensed to-be returned, as already described, to heating element 8 for further conversion.

Vapors from fractionator 11 pass through line 25 and valve 26, are subjected to condensation and cooling in condenser 27, from which distillate and uncondensable gas passes through line 28 and valve 29 to be collected in receiver 30. Uncondensable gas may be released from the receiver through line 31 and valve 32. Distillate may be withdrawn through line 33 and valve 34. A portion of the distillate may, if desired, be Withdrawn from receiver 30 and recirculated by well known means (not shown), to the upper portion of fractionatorll to assist fractionation of the vapors and to maintain the desired vapor outlet temperature'from the fractionator.

Residual oil remaining unvaporized in chamber 22 is withdrawn through line 35 and valve 36 and is introduced into an externally heated rotary retort 37. The coking retort 37 is located in a furnace setting 38 of any suitable form, which may be supplied with flue gases from furnace 16 through duct 39, regulated by damper 40, for the purpose of utilizing waste heat from this source or, if desired, fuel such as oil, gas or pulverized solid fuel, together with an atomizing and combustion supporting medium,'such as air or steam, may be supplied to the furnace through any suitable form of burner 41. It will be understood that retort 37 may, in this manner, be heated either with fresh combustion products or with flue gases or partially by both. Perforated arches 42 and 43, in furnace 38, serve as a means of securing substantially even distribution of heat to the heated shell 76 of the retort. Combustion products may leave furnace 38 through duct 44 to a stack (not shown).

Rotation of the heated shell 76 of the retort, by any suitable motivating means (not shown) operating through a gear arrangement 45, also assists in insuring uniform distribution of heat to the oil undergoing coking, and th's feature, together with the slight inclination of the retort fromthe horizontal toward its discharge end, assists in the continuous removal of coke or carbonaceous material from the discharge end 46 of the retort to a suitable discharge arrangement 47 such as, for example, a helical conveyor. Any suitable means (not shown) such as a scraping or breaking device may be employed to loosen the deposit of carbonaceous material from the heated shell of the retort, permitting its continuous removal from the coking zone or, if desired, the retort may be intermittently allowed to cool or a suitable cooling medium such' as light oil or water may be sprayed onto the deposited carbonaceous material to cool and break it away from the walls of the retort or, if desired, a plurality of coking retorts may be employed which may be alternately operated, one or more being cleaned and prepared for operation while another is in use.

Vapors are removed from the stationary discharge end 46 of retort 37 through line 48 and may pass through valve 49 to condensation and cooling in condenser 50 or, if desired, the vapors may be first passed through line 51 and valve 52 to fractionation in fractionator 53. A suitable cooling agent, such as distillate from receiver 62, or the raw oil charge to the cracking system, may be introduced into the fractionator 53 to assist in controlling fractionation therein. Vapors subjected to fractionation in fractionator 53 are separated into relatively light and relatively heavy components. The latter, which are condensed in the fractionator may collect in its lower portion, passing through line 54 to be withdrawn from the process through line 55 and valve 56 or passing, all or in part, through valve 72 in line 54 to pump 73 from which they are fed through line 74 and valve 75 into line 7 and thence to heating element 8 for further conversion. The relatively light components of the vapors from retort 37, after separation from their relatively heavy components in fractionator 53, may pass through line 58 and valve 59 into line 48 to be subjected to condensation and cooling in condenser 50.

Condensed distillate and gas from condenser 5'0, comprising either all the vapors from retort 37 or only their lighter components, in case they are previously subjected to fractionation, as already described, pass through line 60 and valve 61 to collection in receiver 62. -Uncondensable gas may be released from receiver 62 through line 63 and valve 64. A portion of the distillate may be withdrawn from the receiver to storage or elsewhere, as desired, through line 65 and valve 66. L

The remainder of the distillate collecting in receiver 62, or all of it in case none is withdrawn fro'mthe system, is withdrawn through line 67 and valve 68 to pump 69, from which it is fed through llne 70 and valve 71 into line 20, commingling in this line with the relatively hot vaporous and non-vaporous products passing from chamber 19 to chamber 22, serving to dilute and cool said products and substantially preventing their further conversion to coke or carbonaceous material.

To enable a more flexible control over the return of reflux and distillate from the coking operation to the cracking operation, I have provided a two-way crossover line 70' provided with cracked constituents moving through line 20 from reaction chamber 19 to low pressure chamber 22 and that on the other hand distillate from line 70 can be fed to line 74 and thence to the charging line 7 of the cracking system.

Pressures employed within the system may range from substantially atmospheric to superatmospheric pressures as high as 2,000 pounds or more per square inch. Conversion temperatures employed may range from 800 to 1200 F., more or less. Preferably, the heating element of the s cracking system utilizes conversion temperatures,

mospheric-pressure is preferably employed in the coking retort and may be substantially equalized in the succeeding fractionating, condensing and collecting portions of the coking system. The temperature to which the residual oil is subjected during coking will depend primarily upon the character of the material supplied to this zone and the desired degree of volatility of the carbonaceous products. Temperatures employed in this zone may range, for example, from 900 to 1600 F.. more or less.

As a specific example of the operation of the process of the present invention, a 24 A. P. I. gravity Mid-Continent fuel oil is subjected in the heating element to a temperature of approximately 890" F. A superatmospheric pressure of approximately '300 pounds per square inch is maintained 11 both the heating element and reaction chamber, A reduced pressure ofapproximately 50 pounds per squareinch is maintained in the vaporizing chamber and in the succeeding fractionating, condensing and collecting portions of the cracking system. Residual oil from the vaporizing chamber is subjected to coking in the rotary retort at a temperature of approximately 1250 F. at substantially atmospheric pressure. Vapors from the coking retort are subjected tofractionation, their relatively heavy components being returned, together with reflux condensate from the fractionator of the cracking system, to the heating element for further conversion while their relatively light components are condensed, cooled and recirculated to the transfer line between the reaction chamber and vaporizing chamber of the cracking system. This operation may produce about 72% of motor fuel having an anti-knock value approximately equivalent to a blend of 15% iso-octane and 25% normal heptane. In addition, about 75 pounds per barrel of charging stock, of relatively low volatile coke suitable, for example, for use as domestic fuel may be produced, the remainder of the charging stock is chargeable to uncondensable gas and loss. When a portion of the distillate from the coking operation is withdrawn from the system as a separate product the yields of all other products are somewhat decreased, particularly the gas and motor fuel yields.

In addition to the relatively high yields of desirable products which may be produced by the process of the present invention from relatively heavy oils'it has the further advantage, due to the provisions for continuous coking of the residual oil and for preventing coking in the line between the reaction chamber and vaporizing chamber of the system that the operating cycle may be greatly extended over that possible in ordinary nonresiduum cracking operations, for example, it may be possible to operate in accordance with the provisions of the present invention for as much as 60 calendar days or more without any substantial decrease in the through-put or yields.

It will be understood that the foregoing examples are given only for the purpose of illustrating certain conditions which may be employed and results obtainable in the operation of the process and that they do not limit the broad spirit and scope of the invention.

I claim as my invention:

1. A cracking process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and thence discharging the same into an enlarged reaction zone maintained under cracking conditions of temperature and pressure, removing vapors and unvaporized oil as a mixture from the reaction zone and flash distilling the same by pressure reduction in a flashing zone, separately removing vapors' and unvaporized oil from the flashing zone, reducing the removed unvaporized oil to coke in a coking zone, condensing the vapors evolved in the coking zone and introducing a portion 'of the resultant condensate, without prior heating thereof to cracking temperature, into the mixture of vapors and unvaporized oil being discharged from the reaction zone into the flashing zone to cool said mixture.

2. A cracking process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and thence discharging the same into an enlarged reaction zone maintained under cracking conditions of temperature and pressure, removing vapors and unvaporized oil as a mixture from the reaction zone and flash distilling the same by pressure reduction in a flashing zone, separately removing vapors and unvaporized oil from the flashing zone, reducing the removed unvaporized oil to coke in a coking zone, fractionating the vapors evolved in the coking zone to condense heavier fractions thereof, returning resultant reflux to the heating zone, flnally condensing the fractionated vapors and introducing at least a portion of the final condensate, without prior heating thereof to cracking temperature, into the mixture of vapors and unvaporized oil being discharged from the reaction zone into the flashing zone to cool said mixture.

3. A cracking process which comprises heating hydrocarbon oil to cracking temperature under pressure in a heating zone and thence discharging the same into an enlarged reaction zone maintained under cracking conditions of temperature and pressure, removing vapors and unvaporized oil as a mixture from the reaction zone and flash distilling the same by pressure reduction in a flashing zone, separately removing vapors and unvaporized oil from the flashing zone, reducing the removed unvaporized oil to coke in a coking zone, fractionating the vapors evolved in the coking zone to condense heavier fractions thereof, returning a portion of the resultant reflux condensate to the heating zone, and introducing another portion of reflux condensate, without prior heating thereof to cracking temperature, into the mixture of vapors and unvaporized oil being discharged from the reaction zone into the flashing zone to cool said mixture.

JOSEPH G. ALTHER. 

